Rate per night far below the calendar standard and non-refundable rates

Hello, 

My standard rate per night is set to 150 EUR and the non-refundable rate is set at 135 EUR. Also, I've setup an additional cleaning fee of 60 EUR/stay.

However, people can book at 48,60 EUR/night and I don't understand how it is possible and where this price per night is coming from. Can you help? 

Please note that I've not set any discount per week/month or any other kind of discount. 

Thanks in advance for your help.